Unlock issues

Bought unlocked iPhone 7 plus from Best Buy and used with MetroPCS carrier for 3 years. Now tried to switch carriers and got notification that SIM not supported per lock. Contacted MetroPCS and T-Mobile to unlock phone with no success. I'm trying to switch carriers to save money monthly and it looks like it may wind up costing me more. New carrier already portal-ed my number over from Metro. Haven't been able to use my phone for 2 weeks now. I have iPhone 7 plus and I've confirmed that my iPhone supports the SIM of this carrier. Any ideas what might be happening or how to fix? Apple tells me nothing they can do. I need my phone asap. My customers use this number to contact me to do work.